Naomi McCallion

Positive End Expiratory Pressure during Resuscitation of Premature Lambs Rapidly Improves Blood Gases without Adversely Affecting Arterial Pressure

Positive end expiratory pressure (PEEP) is important for neonatal ventilation but is not considered in guidelines for resuscitation. Our aim was to investigate the effects of PEEP on cardiorespiratory parameters during resuscitation of very premature lambs delivered by hysterotomy at ∼125 d gestation (term ∼147 d). Before delivery, they were intubated and lung fluid was drained. Immediately after delivery, they were ventilated with a Dräger Babylog plus ventilator in volume guarantee mode with a tidal volume of 5 mL/kg. Lambs were randomized to receive 0, 4, 8, or 12 cm H2O of PEEP. They were ventilated for a 15-min resuscitation period followed by 2 h of stabilization at the same PEEP. Tidal volume, peak inspiratory pressure, PEEP, arterial pressure, oxygen saturation, and blood gases were measured regularly, and respiratory system compliance and alveolar/ arterial oxygen differences were calculated. Lambs that received 12 cm H2O of PEEP died from pneumothoraces; all others survived without pneumothoraces. Oxygenation was significantly improved by 8 and 12 cm H2O of PEEP compared with 0 and 4 cm H2O of PEEP. Lambs with 0 PEEP did not oxygenate adequately. The compliance of the respiratory system was significantly higher at 4 and 8 cm H2O of PEEP than at 0 PEEP. There were no significant differences in partial pressure of carbon dioxide in arterial blood between groups. Arterial pressure was highest with 8 cm H2O of PEEP, and there was no cardiorespiratory compromise at any level of PEEP. Applying PEEP during resuscitation of very premature infants might be advantageous and merits further investigation.

Effects of tidal volume and positive end-expiratory pressure during resuscitation of very premature lambs

BACKGROUND Guidelines recommend neonatal resuscitation without controlling tidal volume or positive end-expiratory pressure (PEEP). However, these may improve gas exchange, lung volume and outcome. AIM To investigate resuscitation of very premature lambs with a Laerdal bag without PEEP versus volume guarantee ventilation with PEEP. METHODS Anaesthetized lambs (n=20) delivered at 125 d gestation were randomized to three groups receiving 15 min resuscitation: (1) Laerdal bag and no PEEP; (2) ventilation with a tidal volume of 5 ml/kg and 8 cm H(2)O PEEP; (3) ventilation with 10 ml/kg and 8 cm H(2)O PEEP. They were then all ventilated for 2 h with tidal volumes of 5 or 10 ml/kg, and 8 cm H(2)O PEEP. Ventilation parameters and blood gases were recorded. RESULTS Different tidal volumes affected PaCO(2) within minutes, with 10 ml/kg causing severe hypocarbia. PEEP had little effect on PaCO(2). Oxygenation improved significantly with PEEP of 8 cm H(2)O, irrespective of tidal volume. CONCLUSION Very premature lambs can be resuscitated effectively using volume-guarantee ventilation and PEEP. Tidal volumes affected PaCO(2) within minutes but had little effect on oxygenation. PEEP halved the oxygen requirement compared with no PEEP. Resuscitating premature babies with controlled tidal volumes and PEEP might improve their outcome.

Outbreaks of extended spectrum beta-lactamase-producing Enterobacteriaceae in neonatal intensive care units: a systematic review

Objective To establish the number of outbreaks of extended spectrum beta-lactamase (ESBL) producing organisms in neonatal intensive care units (NICUs), to determine causes, mortality rates, proportions of infants colonised and infected and the interventions that terminated outbreaks. Methods A systematic review of the literature in English, Spanish and French was undertaken with searches in four databases. The review conformed to the PRISMA guidelines, and the data extraction was modelled on the ORION criteria for studies of nosocomial infection. Results 75 studies fulfilled the inclusion criteria. There were 1185 cases of colonisation, 860 infections and 139 deaths. The median outbreak duration was 6.2 months (IQR 2.0–7.5 months). Klebsiella pneumoniae was the most frequently implicated pathogen. Understaffing was the most frequent risk factor for outbreaks. The most commonly identified source was admission of an ESBL-colonised infant with subsequent horizontal dissemination. The main interventions described were improved infection-control procedures and screening of staff and the environment. 26 studies were included in the quantitative analysis. Random effects meta-analysis indicated high mortality rates in infants who developed infection (31%, 95% CI 20% to 43%). Conclusion ESBL outbreaks in NICUs are associated with significant mortality and prolonged disruption. Understaffing is a major risk factor, but is infrequently addressed by interventions. Poor infection-control procedures are frequently implicated as contributing to ESBL spread. Better reporting of outbreaks may help clarify the role for routine ESBL screening in NICUs.

Volume guarantee ventilation, interrupted expiration, and expiratory braking

Background: In volume guarantee ventilation with the Dräger Babylog 8000 ventilator, inspiratory and expiratory flows are monitored and the expiratory tidal volume calculated following each inflation. The pressure for the next inflation is modified to ensure the expired tidal volume is close to the set value. Aim: To investigate interrupted expiration observed during volume guarantee ventilation of spontaneously breathing, ventilated infants. Methods: Spontaneously breathing infants, ventilated with volume guarantee, had recordings of gas flow, ventilator pressures, tidal volume waveforms, oximetry, heart rate, and transcutaneous oxygen and carbon dioxide during 10 minute recordings. Results: A total of 6540 inflations were analysed from 10 infants; 62% were triggered. Two different patterns were found: (1) Normal volume guarantee pattern with 97% of triggered and 91% untriggered inflations. It had a normal expiratory curve and a mean expired tidal volume within 3% of the set volume, but a large variation due to the babies’ breathing. (2) A pattern of interrupted expiratory flow after ∼3% of inflations due to a small inspiration (∼1.3 ml/kg) during expiration. This led the ventilator to calculate an inappropriate total expired tidal volume for that inflation and an increase in the pressure for the next inflation. Conclusions: After about 3% of inflations, with volume guarantee ventilation, interruption of the expiration causes an increased pressure for the next inflation of ∼4.9 cm H2O, compared with normal volume guarantee inflation. The interrupted expiration is most likely to be due to diaphragmatic braking.

Variation in inspiratory time and tidal volume with T-piece neonatal resuscitator: association with operator experience and distraction.

The most recent Neonatal Resuscitation Programme (NRP 5th edition) guidelines recognise the T-piece resuscitator (Neopuff) device as an acceptable method of administering a pre-selected peak inspiratory pressure (PIP) and positive end expiratory pressure (PEEP). While these are constant, other parameters are operator-dependent. Although in widespread clinical use, there is little published data on the use of the T-piece resuscitator in neonatal resuscitation. This study showed that despite fixed inflating pressures, less experienced operators used prolonged inspiratory times. Wide variation in mean airway pressure and tidal volume were seen in all operators.

Serum albumin and mortality in very low birth weight infants

Serum albumin is a predictor of outcome in adults but its role in paediatric patients is unclear. Earliest albumin was not associated with mortality or morbidity in very low birth weight (VLBW) infants. However, the lowest serum albumin had a statistically significant inverse correlation with mortality and potentially plays a prognostic role in VLBW neonates.

Serial measures of cardiac performance using tissue Doppler imaging velocity in preterm infants < 29 weeks gestations

INTRODUCTION Tissue Doppler imaging (TDI) is a useful marker of myocardial performance in preterm infants. We aimed to demonstrate serial changes in TDI velocity in preterm infants <29weeks gestation, to assess the impact of inotropes and a haemodynamically significant patent ductus arteriosus (hsPDA). METHODS This was a prospective observational study of preterm infants <29weeks gestation. Echocardiography was performed at days 1, 2, 5-7 and at 36weeks, or before hospital discharge. Infants with hsPDAs on day 5-7 and those who received inotropes in the first week of life were not included in the Reference Cohort. Systolic (s`) and diastolic (e` and a`) velocity waves were assessed at the mitral and tricuspid annulus and basal septum. RESULTS One hundred and thirty nine infants with a mean (SD) gestation and birthweight of 26.7 (1.5) weeks and 946 (247) grams were enrolled. The 66 infants (47%) in the Reference Cohort demonstrated an increase in functional parameters with increasing age [LV s`, Septal s`, and RV s`, Day 1-36weeks: 2.8 (0.6) to 4.7 (1.0), 2.4 (0.6) to 4.6 (0.8), 3.6 (0.6) to 6.9 (1.0) cm/s respectively; all p<0.05). The 24 infants who received inotropes had lower LV e` [2.9 vs. 3.6cm/s], Septal e` [2.3 vs. 2.8cm/s] and a` [3.2 vs. 3.9cm/s], and lower RV a` [3.3 vs. 3.9cm/s] on Day 1 (all p<0.05). Fifty five infants had a hsPDA on Day 5-7, demonstrating higher LV [4.7 vs. 4.0cm/s] and Septal e` [3.9 vs. 3.3cm/s], and a higher LV E/e` [13 vs. 10] (all p<0.05). CONCLUSION Extremely preterm infants display a gradual increase in tissue Doppler velocities from birth until 36weeks corrected age. The presence of a hsPDA increases diastolic TDI velocities. Infants requiring inotropes have lower diastolic myocardial velocities on Day 1.

The Effect of a Significant Patent Ductus Arteriosus on Doppler Flow Patterns of Preductal Vessels: An Assessment of the Brachiocephalic Artery

&NA; Systemic hypoperfusion secondary to a patent ductus arteriosus (PDA) is thought to only affect post‐ductal vessels. In a prospective observational study of 51 preterm infants, we demonstrated that a persistent PDA by day 5‐7 is associated with reversed diastolic flow in the brachiocephalic artery when compared with those without a PDA.

Left ventricular rotational mechanics in infants with hypoxic ischemic encephalopathy and preterm infants at 36 weeks postmenstrual age: A comparison with healthy term controls.

There is a paucity of data on left ventricle (LV) rotational physiology in neonates. We aimed to assess rotational mechanics in infants with hypoxic ischemic encephalopathy (HIE) and premature infants (<32 weeks) at 36 weeks postmenstrual age (PMA) (preterm group) and compare them with healthy term controls (term controls). We also compared the parameters in preterm infants with and without chronic lung disease (CLD).

The impact of a hyperdynamic left ventricle on right ventricular function measurements in preterm infants with a patent ductus arteriosus.

Background and aims Right ventricular (RV) functional assessment in premature infants includes basal longitudinal strain (RV BLS), RV systolic tissue Doppler velocity (RV s′), tricuspid annular plane systolic excursion (TAPSE) and RV fractional area change (FAC). A hyperdynamic left ventricle (LV) may influence RV measures of displacement (TAPSE) and velocity (RV s′) but not measures of relative change of length (RV BLS) or area (FAC). We aimed to explore this hypothesis in preterm infants with a patent ductus arteriosus (PDA). Methods We measured LV function (ejection fraction (LV EF); left ventricular output) and RV function (RV BLS; RV s′; TAPSE; FAC) on days 1, 2 and 5–7 in infants <29 weeks. The cohort was divided based on PDA presence by days 5–7. LV and RV function measurements were compared between the groups using two-way analysis of variance with repeated measures. Results 121 infants with a mean (SD) gestation and birth weight of 26.8 (1.4) weeks and 968 (250) g were enrolled. By days 5–7, the PDA remained open in 83 (69%), with evidence of hyperdynamic LV function. There was no difference in RV s’ (5.3 (0.9) vs 5.1 (1.0) cm/s, p=0.3) or TAPSE (6.2 (1.3) vs 6.1 (1.2) mm, p=0.7) between infants with and without a PDA, but infants in the PDA group had lower RV FAC (41 (8) vs 47 (10) %, p<0.01) and lower RV BLS (−24.2 (5.0) vs −26.2 (4.1) %, p=0.03). Conclusions LV influence on RV functional parameters must be taken into account when interpreting of RV function using those techniques.